The present invention relates to a flexible tool for handling small objects, as well as a method for handling small objects using the flexible tool. The flexible tool comprises one or more mini robots, fast measurements of robot positions and feed back to a computer system controlling the mini robots. The computer system further comprises vision and motion planning.
In connection to the increasing miniaturising of almost all high-tech products, handling of small components is getting increasingly important. Many modern high-tech products comprise one or more very small components. There are in general two ways of producing products with very small parts.
One is to make the assembly by hand using a microscope and special handheld tools. Hand held assembly is prone to human errors, and furthermore it is expensive. Due to the cost, human assemblies are often made in countries with low salaries and this seldom has a positive effect on the yield. Furthermore, only smaller numbers of products may be produced in this way.
Another possibility is to construct an assembly machine dedicated to do the taskxe2x80x94or one of several tasks. A special machine is rather expensive, and therefore only an option if it is used for high-volume production. It may be very difficult or even impossible to change to new demands when the product or market chances. Furthermore, the time from a new special assembly tool is required to it may be ready for use could easily be far to long. There is therefore a strong need for a possibility of producing small and medium sized number of products using a flexible tool. The tool should be easy to handle and fast to set up for new products.
When handling small components, it is usually very important to handle them with a high degree of precision. A standard robot can usually not handle and position components with a sufficiently high degree of precision. Standard robots use incremental decoders in each joint. Each of the encoders has certain accuracy, and the accuracy must be added to get the accuracy of the robot. When a component is to be picked up or positioned, the computer controlling the robot calculates the movements necessary for doing the task. However, due to the accuracy of the decoders, the calculated position may be several 10th of millimetres off.
U.S. Pat. No. 6,024,526 discloses a unit for use in testing semiconductor components. The unit is designed to manipulate either packaged semiconductor components or semiconductor wafers and present them to a test head. The integrated unit includes a positioning mechanism with a tool plate that can be changed to grasp either a semiconductor wafer or a tray of semiconductor components. The tool plate uses a vacuum plate. To hold a tray of semiconductor parts, the vacuum plate has numerous independently operable holes. Each hole is positioned behind one semiconductor component and can be engaged or released separately so that the components can be sorted into separate output bins. To hold a wafer, the tool plate has an extendible tongue member that can be inserted into a stack of semiconductor wafers to pick up one wafer in the stack.
The use of vacuum for holding and moving components is less useful when the components are small, since the precision when picking up and when releasing small components is not sufficient. Furthermore, when using vacuum it is difficult to ensure that the orientation of the components is correct, when picking them up.
It is an object of the present invention to provide a flexible tool for handling small objects with a high degree of precision. The tool being capable of moving objects, positioning the objects at the required position and carrying out one or more operation(s) on the objects with high accuracy.
According to the present invention, the free-arm robot is used to move the hexapods. For this task, the accuracy is appropriate. When the hexapods are positioned in their docking stations, they are in a very stiff and good controlled environment, and the accuracy can therefore be very high. Furthermore, a telemetric system including vision by CCD-cameras provides real-time information regarding the progress of the handling of the components and feedback to the controller. In other words, the present invention combines the flexibility of the free-arm robot with the high accuracy of the fixed hexapods and real-time feedback from the vision system.
According to a first aspect of the present invention there is provided a flexible tool for handling small objects, the tool comprising:
a free arm robot,
at least one hexapod for handling small objects,
an internal workspace for performing operations on small objects, and
an external workspace for storing small objects during non-operation,
said at least one hexapod(s) being adapted to engage with a small object and to move a small object between said internal workspace and said external workspace, and said free arm robot being adapted to move the at least one hexapod(s).
According to a second aspect of the present invention there is provided a flexible tool for handling small objects, the tool comprising:
a conveyer belt,
at least one hexapod for handling small objects,
an internal workspace for performing operations on small objects, and
an external area for holding small objects during non-operation,
said conveyer belt being adapted to move a small object between said internal workspace and said external area and said at least one hexapod(s) being adapted to perform one or more operation(s) on said small object, when said small object is positioned within said internal workspace.
According to a third aspect of the present invention there is provided a method of handling small objects using a flexible tool, the method comprising the steps of:
moving one or more small object(s) to be handled from an external workspace to an internal workspace of the flexible tool using one or more hexapod(s),
performing operations on said small object(s) in the internal workspace using said hexapod(s).
The system platform is the base of the system. The platform comprises a cube and an external workspace each of which comprises docking stations for up to six hexapods. At each of the 12 docking stations a hexapod may be positioned and locked. When locked, the hexapod is connected to the main computer and to a power supply. A total of up to 11 hexapods may work at the same time in the system.
The platform further comprises six supply units for supplying components to be handled in the cube, or for storage of components that has already been handled. These components can be objects on which operations are carried out and can be tools to be used by the hexapods for carrying out these operations. At each of the supply units, a docking station is provided. The supply units may revolve so as to position new components within reach of the hexapod. The components are positioned with a know orientation in containers easily handled by the hexapod.
The floor of the cube may be one or more extra supply units, or it may be one or more conveyer belts or similar. The floor is adapted to move objects from outside the cube to a position inside the cube, where it may be handled by the hexapods.
A free-arm robot is positioned above the platform and connected to the platform in a stable manner. The robot may reach all the hexapods in any of the positions in the cube of the external workspace. It may move the hexapods from one position to another simply be selecting them and xe2x80x9csnap-lockingxe2x80x9d them onto an adapter at the tip of the robot arm. When the hexapods is positioned at one of the docking stations, it is connected to a power supply and to the main computer by a number of data lines.
The system platform is made of a very stable and solid material, isolating the platform from most vibrations and other undesired environmental influences. The complete system is prepared for working in a clean-room environment.
The hexapod is construed as a slack-free construction with motors such as linear motors, step-motors, DC-motors with encoder, magnetic linear motors or hydraulic motors positioned outside the working area. The ball joint between the linear motor and the base plate is designed as spring forced ball resting on 3 angled surfaces, securing a determent positioning. This design allows the ball to have a large spherical diameter tolerance and still both have a smooth and slack free movement.
The flexible joint at the tool end of the hexapod is designed using a wire made from NiTi-alloy, better known as memory metal. This design is both simple and allows the joint, at the same time, to be both flexible and slack free.
The linear motor may be designed as an inchworm piezo motor. In this design the locking and moving piezo elements are separated parts. Use of the inchworm concept gives a design with no torque from the action of the motor, allowing a more simple design of the flexible joints of the hexapod. The separation of the locking and moving piezo elements makes it possible to design the motor so that it automatically locks the piston when the power is removed. This is an important feature in a system where the hexapods are moved without power from one position to another by a standard free-arm robot. Furthermore, the design of the motor allows the piston to be submitted to larger radial forces than the currently known inchworm piezo motor designs.
As an alternative to the use of inchworm piezo motor, step-motors, DC-motors with encoder, magnetic linear motors or hydraulic motors or others can be used. A suitable step-motor could be a step-motor having a step smaller than 1 degree, such as 0.72 degree.
The docking adapter of the hexapod is adapted to be locked into the counterpart adapter of the docking station.
When a hexapod is to be inserted into a docking station the free-arm robot positions the hexapod so that the docking adapter of the hexapod locks into the docking station. When the two adapters have locked, the free-arm robot releases its grip and retracts from the hexapod. Hereafter the docking station connects the power and data lines, and the hexapod is ready for use (hot pluck-in).
When a hexapod is to be removed from a docking station, the free-arm robot locks it""s grip on the hexapod whereby the power and data lines to the hexapod are disconnected. When the free-arm robot pulls backwards, the hexapod docking adapter is released from the docking station adapter. The hexapod is thereby free to be inserted into another docking station.
Using the hexapod in combination with the computer vision systems and the telemetric systems is possible to move objects to a desired position with a high degree of precision. During movements, the computer vision and telemetric systems provide information to the motion planner regarding the position and orientation of the objects and on the tools used due to the position of the camera. This information is compared to information regarding the desired positions, and an eventual error may immediately be corrected by transmitting commands to the hexapod controller.
The feedback system is updated at very high frequencies. In a preferred embodiment, the update frequency of the telemetric system is app. 200 Hz, and the computer vision systems update the output at 25 Hz.
The cube is the heart of the system and is placed at the centre of the system platform. The cube is shown in FIG. 5.
The cube is a very stable and stiff environment in which the hexapods may be positioned. The cube is constructed to remove any influence from the environment, e.g. electronic noise, vibrations from the environment and air borne (sound pressure), and temperature. When a hexapod is moved from one docking station to another, the movement is not very precise. This is not necessary, as the hexapod is not involved in any processes or assemblies. When the hexapod is positioned in a docking station in the cube, it is positioned in a very well defined and very stiff environment.
In the cube the assembly and processing is made.
The cube comprises
A floor adapted to hold one or more components or parts of the assembly. The floor may be a conveyer belt or similar adapted to transport small objects from outside the cube into the cube. The components may also be transported out of the cube again after use.
A number of docking stations for holding up an equal number of hexapods. Each docking station is positioned at an angle above the floor pointing towards the centre of the cube. The docking stations provide power supply and data lines to the main computer. In a preferred embodiment, the number of docking stations is six.
A video camera positioned at the top of the cube for surveillance and vision purposes.
A number of telemetric systems adapted to interact with the hexapods when present. Preferably, the number of hexapods and telemetric systems should be the same.
A number of inlets for providing laser light, glue or similar to the process taking place inside the cube.
A tool station for providing tools to be used in the assembly or process, which takes place inside the cube. The tool station could be a turntable with a number of different tools ready for being picked up by a hexapod. The tools may comprise a pipette for dispensing glue or other fluid, drills, a light source with UV-light, etc. Furthermore, a variety of tools may be positioned together at a revolving tool-holder, this tool-holder being ready for being picked up by a hexapod.
The docking station is a station for holding a hexapod.
The docking station provides power supply to the hexapod as well as a data line to the main computer. Furthermore, it may provide a data line from the transmitting part of the telemetric system to the calculating part of the telemetric system.
The docking station is formed as an adapter suited to lock onto the counterpart adapter (docking adapter) on the hexapods.
When a hexapod is to be inserted into a docking station the free-arm robot positions the hexapod so that the docking adapter of the hexapod locks into the docking station. When the two parts have locked together, the free-arm robot releases it""s grip and is retracted from the hexapod, the docking station connects the power and data lines, and hereafter the hexapod is ready for use (hot pluck-in).
When a hexapod is to be removed from a docking station, the free-arm robot locks it""s grip on the hexapod whereby the power and data lines are disconnected. When the free-arm robot pulls backwards, the hexapod docking adapter is released from the docking station adapter. The hexapod is thereby free to be inserted into another docking station.
There are a number of telemetric systems in the systemxe2x80x94one for each hexapod operating in the cube.
A telemetric system comprises three main parts.
The first part is positioned at the tip of the hexapods, and is called the transmitting part. The transmitting part comprise five optical transmitters positioned relative to each other as the dots on the xe2x80x9cnumber 5xe2x80x9d on a die, but with the modification that the centre dot is elevated relative to the other 4 dots.
The optical transmitters may be turned on and off in a predetermined sequence. Light Emitting Diodes (LED) may be used as optical transmitters, but in stead of LED""s, optical fibres may be used for providing the light sources. Furthermore, the transmitting part comprises a small printed circuit board comprising a microprocessor and several data lines to the calculating part of the telemetric system. The transmitting part further comprises control for the optical transmitters. In case of using optical fibres as optical transmitters, LED""s would be positioned on the transmitting part together with the other end of the optical fibre
The second part is positioned at the cube, and is called the receiving part. This part comprises a beam splitter and two cylindrical lenses. Each of the lenses, positioned after the beam splitter, directs an image of the transmitting part towards two CCD-cameras, where an image is created. The first CCD-camera is rotated 90xc2x0 in relation to the other. Alternatively, a two-dimensional CCD-camera may be used.
The third part is the calculating unit. The calculating unit controls the transmitting part by turning on and off the LED""s in a predetermined sequence. It also controls the receiving part by acquiring images of the transmitting part with the LED""s turned on. Using two sets of three images with each their LED turned on, the calculating unit is able to
Determine the distance between the transmitter and receiver
Determine three different angles of rotation of the transmitting part relative to the receiving part
Determine a parallel shift in two directions of the transmitting part relative to the receiving part
The amount of data generated by a telemetric system is rather large. Each set of data comprises six CCD line scans each comprising at least 2048 pixels. For each of these line scans, data must be analysed and information extracted. The information extracted must be combined with information from the other five line scans. The result is a set of co-ordinates defining the position and orientation of the transmitting part relative to the receiving part.
As the transmitting part is positioned at the tip of the hexapods, it is the position of the tip relative to the receiving part that may be determined using the telemetric system. The tip of the hexapod will usually hold a component or tool in a well-known manner, and the position and orientation of the component or tool may therefore be determined.
If the main computer of the system should receive the primary data from the CCD line scan cameras, it would be overloadedxe2x80x94especially if there is a large number of telemetric systems active. As the main computer only need the set of co-ordinates, the calculating unit is adapted to do the calculations. The output from the calculating unit is the set of co-ordinates.
The update frequency of the telemetric system may be up to several hundred Hertz.
In connection to each of the docking stations in the external workspace an additional telemetric system may be provided. This will promote safe and problem free handling of the components in the external workspace.
The main computer is preferably comprised by a high performance PC, as it has a large number of tasks to do. To relieve the main computer a number of low level processors are provided.
The main computer is the Graphical User Interface (GUI) to the user. This means that all information from the system to the user and vice-versa is handled by the main computer. Using the graphical interface new parts, processes and assemblies are defined, and these may be combined to designs. Designs may be simulated using the main computer, or they may be xe2x80x9crunxe2x80x9d by the system.
Running a design on the system comprise control of the free-arm robot, one or more hexapods, one or more telemetric systems, as well as one or more vision systems. Further, it comprises motion planning, so that the hexapods do not collide, and display on the GUI of the progress of the process.
When running a design, the computer receives information from the telemetric systems and the vision systems. Using this information, the computer then calculates the positions of the components in the cube as well as in the external workspace, and determines which actions to do next.
From the users point-of-view, the system may be divided into 3 modes.
Object mode. In this mode, objects, assemblies, and processes are defined using a Graphical User Interface (GUI). After definition, they are stored in a central database.
Design mode. Object, assemblies, and processes defined in the object mode may be combined into designs, which may be simulated in the computer and xe2x80x9crunxe2x80x9d by the Microbotic system.
Calibration mode. Mechanical configuration and calibration of the system. Mechanical configuration involves changing hexapod tools and other preparations. Calibration is essential for upholding the desired accuracy of the system and is only performed by an expert user.
The control of objects involves e.g. a number of hexapods, video cameras (vision systems) and telemetric systems as well as motion planning of the free-arm robot and hexapods. Another important task is to provide a GUI for the user of the system.
From the programmers point-of-view, the system may be divided into 3 layers.
User layer. The user layer provides the GUI of the system.
High level layer. The high level layer is to be considered as a kernel completely transparent to the user. It is centred on a database that comprises CAD models for work pieces and descriptions of how to process these.
Low level layer. The low-level layer is not part of the main computer as such. The low-level layer is provided by a number of systems taking care of one task only. The low-level tasks are e.g. the calculations made in the calculating part of the telemetric systems. The main computer system does however control the low-level layer as it sends commands to the layer and receives information from the layer.
A system capable of handling these demands is necessarily very complex. The software architecture is therefore divided into clearly separated parts, which are all open, expandable and easy to understand and maintain. The various system components interact with each other as outlined in FIG. 7.
In the external workspace there are six supply units for storage of components to be used inside the cube or assemblies that has been made inside the cube. Each of the six supply units is positioned adjacent to an external docking station. In combination to each of the docking stations there may be a telemetric system.
Each of the supply units comprises a number of containers for storage of a component. The supply unit is adapted to be rotated so as each of the containers in turn may come within reach of a hexapod locked into the docking station.
One or more of the supply units may be shared with other systems. Thereby it is possible to have a line of systems each performing one or more tasks on an assembly and passing the result on to the next system in the line.